Effect of lead exposure on mRNA expression of NMDA receptors in zebrafish embryos and larvae

AIM:To investigate the effect of lead exposure on mRNA expression of N-methyl-D-aspartate(NMDA) receptors in zebrafish embryos and larvae. METHODS:Zebrafish embryos(wild type; AB line) were exposed to lead acetate(PbAc) at concentrations of 0, 0.1, 0.5, 2.5 and 12.5 μmol/L, respectively. Total RNA was extracted from zebrafish embryos or larvae at the time points of 24, 48, 72, 96 and 120 hours post fertilization(hpf). The mRNA levels of NR1.1, NR1.2 and NR2B were determined by real-time quantitative PCR. RESULTS:The mRNA expression of NR1.1, NR1.2 and NR2B gradually increased during embryonic development, raised rapidly at 72 hpf, peaked at 96 hpf(vs that at 24 hpf, P<0.01), and still kept in high level at 120 hpf in control group. The impact of lead exposure on the mRNA expression of NR1.1, NR1.2 and NR2B varied with lead concentrations. With the increasing concentrations of PbAc, the mRNA expression of NR1.1 generally increased and reached the highest level ahead of 96 hpf. The peak mRNA level of NR1.1 was observed at 72 hpf under the condition of PbAc exposure at the concentrations of 2.5 and 12.5 μmol/L, and were higher than that in control group(P<0.05). Similarly, the mRNA levels of NR1.2 and NR2B showed an increasing trend with PbAc exposure. However, the peaking time of NR1.2 and NR2B in mRNA expression spanned from 72 to 120 hpf. The significant correlations between the expression levels of NR1.1, NR1.2 and NR2B were observed(P<0.01) and the Pearson’s correlation coefficient values of r_NR1.1-1.2, r_NR1.1-2B and r_NR1.2-2B were 0.681, 0.637 and 0.514, respectively. CONCLUSION:The mRNA expression of NR1.1, NR1.2 and NR2B gradually increases throughout the embryonic development of zebrafish and reaches the highest levels at early stage of larva. Close correlations between the mRNA expression of NR1.1, NR1.2 and NR2B are present during the period of embryo and larva. Lead exposure induces up-regulation and forward shift of NR1.1, NR1.2 and NR2B at mRNA level, indicating that lead induces abnormal expression of NMDA receptors.